This application claims priority from French patent application 01.08745, filed on Jul. 2, 2001, the entire disclosure of which is incorporated herein by reference.
1. Technical Field
Many areas of industry have to cope with the problem of conveying fluids in systems comprising tubular parts coupled together, whether permanently or temporarily, these parts consisting in some cases of flexible pipes or lines, usually elastomeric in nature (often silicone), which may or may not be reinforced with a textile structure such as a braid incorporated into their walls.
The present invention has to do with a novel type of reusable coupling that can make such a connection.
2. Prior Art
Generally speaking, such connections are made by inserting a nipple into the end of the tube which is then crimped by an outer ferrule so that the wall of the tube is sandwiched between the two, and the nipple provides a support for the coupling parts of the mating means mounted at the outlet or inlet of the assembly to which the pipe is to be connected.
Such an approach, which is found for example in U.S. Pat. No. 3,549,180 and FR 1 385 084, nonetheless has drawbacks in that the presence of a nipple inserted into the pipe significantly reduces the fluid pathway at this point, thus not only disturbing the movement of the fluid but possibly also, in some cases, resulting in a retention of the fluid.
The Applicant has proposed a solution in accordance with the teachings of the abovementioned documents by which this problem can be solved. This solution is illustrated in the accompanying FIG. 1 and provides almost perfect continuity of the inside wall of the tube with the inside surface of the coupling nipple.
In general terms, referring to this FIG. 1, to make the coupling of the end of the tube (1), a nipple denoted by the general reference (2) is inserted into its end. The outer portion (3) of the said nipple forms an annulus designed to support the means (J) for forming the joint with the part to which the pipe is to be coupled.
This done, a peripheral ferrule (4) is then crimped around the tube (1), thus fitted with the nipple (2), thus imprisoning the wall of the tube.
To ensure precise positioning, the ferrule (4) comprises an inward annulus (5) capable of fitting into a peripheral groove (6) on the external surface of the nipple (2) during the crimping operation.
Although such an approach makes it possible to produce couplings in which the internal pathway includes no region of fluid retention, it is not possible to guarantee that the assembly is completely aseptic, owing to the fact that mould, bacteria and the like may sometimes settle in the connection region between the nipple (2) and the end (5) of the ferrule (4).
In its patent application WO 00/01974, the Applicant proposed a solution which not only makes it possible to produce a coupling that contains no region of fluid retention but which also makes it possible to obtain a completely aseptic assembly that eliminates all risk of infiltration from the outside of bodies such as mould, bacteria and the like, which could contaminate the fluid conveyed inside the system. This solution consists, in general terms, in interposing a peripheral seal between the extreme edge of the annulus of the ferrule and that of the outer wall of the groove provided on the nipple.
Such a solution is perfectly satisfactory in the case of fixed systems, but as it involves crimping, it cannot be used to produce couplings that can be disassembled rapidly, for example if a defective pipe requires changing. Moreover, by its very design, such a coupling cannot be reused.
The solution to this problem of producing a reusable, anti-binding and aseptic coupling is to be found in the teachings of French Patent 2 766 901 by the Applicant.
Although this solution is satisfactory in the case of non-reinforced plastic pipes whose walls can be compressed relatively easily, it is unsuitable for producing couplings for the ends of pipes having thick, virtually incompressible walls containing a reinforcement.
To date, therefore, when making couplings on such thick-walled reinforced pipes, only crimped assemblies, of the type disclosed in WO 00/01974, provide mechanical characteristics that eliminate all risk of tearing, and eliminate the problems of retention and the risk of infiltration of contaminants from the outside.
In general terms, the invention therefore seeks to solve all the abovementioned problems while allowing the coupling to be assembled directly by the user in situ and the coupling component to be rapidly dismantled, as for example during a maintenance operation, whilst at the same time allowing it to be reused.
In general terms, the invention therefore relates to a reusable coupling adaptable to the ends of a tube and which comprises:
a nipple comprising a toothed end designed to be inserted into the tube, its inside diameter corresponding approximately to the inside diameter of the tube, the said end being continued by an annular surface external to the tube, at the end of which are the actual means of connection to the part to which the tube is to be connected;
a peripheral ferrule mounted around the tube and imprisoning the latter in engagement with the toothed part of the nipple, the said ferrule comprising an inward annulus capable of fitting into a peripheral groove on the surface of the nipple, while a seal is provided at the location of this annulus.
The coupling according to the invention is characterized in that the peripheral locking ferrule is radially compressible and is immobilized and fixed to the periphery of the tube by a xe2x80x9cconnectionxe2x80x9d assembly comprising two connectable parts mounted around the end of the tube on either side of the said locking ferrule, namely:
a first part or xe2x80x9couter sleevexe2x80x9d positioned around the nipple and comprising on its rear face an annulus capable of bearing against one of the ends of the clamping ferrule and, on its front face, an internal cage forming a nut;
a second part or xe2x80x9cclamping ringxe2x80x9d positioned around the pipe, downstream with respect to the clamping ferrule, the said ring comprising an external threaded portion that can be screwed into the threaded portion of the first part and an internal chamber capable of bearing against the peripheral surface of the ferrule, thereby crushing it and imprisoning the wall of the pipe, as well as pushing the inward annulus of the said ferrule into the peripheral groove on the surface of the said nipple, and imprisoning the seal between the said annulus and the bottom of the groove.
Materials from which the various parts of which a coupling according to the invention is composed can be made are preferably stainless steel for the nipple and the outer sleeve of the connection assembly, while the radially compressible peripheral ferrule and the clamping ring forming the second part of the connection assembly will be made in an engineering plastic.
Such a combination of materials eliminates any risk of binding during assembly and disassembly.
In a preferred embodiment, the compressible ferrule is made of plastic and comprises teeth on its internal face and along part of its length, its external surface having two oppositely tapering regions, the region facing the internal surface of the clamping ring bearing against a region of corresponding taper provided in the chamber of the said ring.
To make the said ferrule radially compressible, staggered slits are provided occupying at least part of the length of each tapering region of the compression ferrule.